In "The Black Cat" By Edgar allen poe. How does Plot, character, point of view, setting, and style support the authors THEME?

The first
step would be to identify the theme.  A theme is a life-truth that the author is trying to share
with his/her audience.  For this story, the theme could be "familiarity breeds
contempt," "justice will prevail," or "you cannot hide the
evil within."  There are certainly others, based on how the story speaks to
each reader, but I find these to be prevalent.

If we choose the last theme,
"you cannot hide the evil within," you can apply all the literary elements you have
identified.

The plot is about a man who changes
from being loving to animals and people, to being one consumed by hatred for both.

This, too, covers the character of the man.  He has been
loving of animals for his entire life; he meets and marries a woman with similar feelings.  As
time goes by, he loses touch with this aspect of himself, loses all patience and compassion, and
resorts to torture, and ultimately, committing murder.

Point of
view is important with this theme because it is only by being able to look into
the very mind and soul of our narrator (from a first person point of view)
that we can not only witness his degradation as a person (drunkenness, abuse, etc.), but we can
also watch (and listen to) how his obvious psychosis permeates his entire being and destroys the
kindness and gentleness that once resided within.

In terms of the
setting, a great deal of the dark side of the story occurs in
"dark" places.  The establishments he haunts each evening are vile.  It is there that
he becomes repeatedly drunk, and it is there that his soul begins its deterioration.  The other
specific setting of the story is the basement of his home: a dark, chilling stage on which the
narrator plays out his final, maniacal act of hatred, and his attempt to cover his
actions.

An author's style is the way he/she
writes, how he expresses himself, grammatical structure, and even the specific words he chooses
to create his own particular way of writing.

Poe's style is very specific to
his writing.  It lends itself to creating horror stories.  Those who remember Alfred Hitchcock
will note that his stories, on TV or in the movies, always created a sense of horror. A more
contemporary parallel would be Stephen King, though his style diverges greatly between stories
such as Carrie, and others like The Shawshank Redemption or The
Green Mile. In all of these cases, the stories are told in such a way as to elicit a
contrived response: we are to be horrified, even fascinated, and certainly drawn in by the
writing style.

When studying , the words Poe chooses to
create a sense of suspense, shock and even revulsion stand out: dread, felon, terror,
horror, gallows and perverseness (both in capital letters),
rabid, and death are words that set a specific mood
and purpose for the reader: to bring about horror and fear.  With these words, the theme is
clear: you cannot hide the evil that lies within.  With the end of the story, the cat (the one
in the title? who knows?) does, in fact, reveal the evil hidden within the
man.